Tuesday, September 06, 2016

Scientific publication in Marine Biology - Ecophysiology team

Global warming affects the abilities of reef-building corals to take up essential nutrients for their survival

Coral reefs are increasingly threatened by warming surface waters, leading to unprecedented alterations of the biogeochemical cycles of marine ecosystems. Sustained periods of high seawater temperature can also disrupt the coral-algal association resulting in massive coral bleaching, i.e : the loss of the symbionts and/or the associated photosynthetic pigments of the organism. As symbiotic algae are the first food providers to the symbiosis, their loss during bleaching may limit the animal’s nutrition.

Researchers of the Ecophysiology team conducted controlled experiments on hard corals as well as on the soft-pulsating species Heteroxenia fuscescens (image below). They showed that some species stopped taking up nitrogen during periods of thermal stress, therefore decreasing their capacity to protein repair and their survival. Conversely, most coral species increased their uptake rates of inorganic phosphorus while thermally-stressed. Phosphorus was indeed an essential nutrient that maintained coral metabolism and the nutritional exchanges between the symbionts and their coral hosts during thermal stress.

Furthermore, the unique rythmic pulsations of Heteroxenia fuscescens allowed this coral species to overcome thermal stress, by keeping constant rates of nutrient acquisition, sustaining the algal symbionts and the whole symbiotic association. These results shed light on how climate alteration may affect the nutrition capacities of reef corals and their survival in the near future.